1. Field
Apparatuses and methods consistent with exemplary embodiments relate to finding an optimal zooming speed, and more particularly, to determining optimal zooming speeds at respective positions of a zoom lens without deteriorating zoom tracking performance.
2. Description of the Related Art
Zoom tracking refers to movement of a zoom lens while maintaining a set focus. In other words, if a zoom lens moves, a focus lens moves together with the zoom lens to maintain a set focus.
If only a zoom lens moves and a focus lens does not move when focus is already set, a focus value determined based on a position of the zoom lens and a position of the focus lens is changed, and thus the focused object is defocused. Therefore, when a position of the zoom lens is changed, a position of the focus lens has to also be changed. If a focus lens does not move until a moving zoom lens is fixed, a longer period of time is taken to set a focus. Therefore, a zoom tracking function for respectively changing a position of the zoom lens and a position of the focus lens at a same time while maintaining a set focus is used.
Zoom tracking methods include a zoom tracking method using locus data and an auto zoom tracking method. The zoom tracking method using locus data may be used for easy zoom tracking by using locus data unique to properties of a lens when information about a distance to an object is known before a zoom lens moves. However, it is necessary to obtain information about a distance to an object in advance and, if information about a distance to an object is incorrect, the object is defocused and it is difficult to re-set focus on the object.
The auto zoom tracking method is a method of embodying zoom tracking when information about a distance to an object is unknown. According to the auto zoom tracking method, zoom tracking may be performed even if information about a distance to an object is not stored in advance. However, a field of view and exposure are changed as a zoom lens moves, and thus a focus value for auto focusing is continuously changed, and it is not technically easy to appropriately adjust the moving speed of a zoom lens based on a position of the zoom lens to maintain a set focus.
In the auto zoom tracking method, a speed calculated via a test is applied to each position of a zoom lens as a speed of changing a position of the zoom lens (referred to hereinafter as a ‘zooming speed’). Here, as a zoom lens located at high zoom power moves toward higher zoom power, a range to move a focus lens in correspondence to movement of the zoom lens is rapidly widened, and thus it is necessary to rapidly reduce a zooming speed by taking into account the widened range to move the focus lens.
As described above, if a zooming speed is rapidly reduced when a zoom lens is moved toward higher zoom power, zoom tracking performance may be maintained, but it is difficult to satisfy a demand for fast zooming speed. Furthermore, since a zooming speed in each position of a zoom lens calculated using a method in the related art always utilizes values calculated via a test during a development stage, a long period of time is taken therefor, and a calculated zooming speed based on a position of a zoom lens may not allow to maintain a consistent performance